Extent Of Nitrification Research Articles

Electrochemical In Situ pH Control Enables Chemical-Free Full Urine Nitrification with Concomitant Nitrate Extraction.

Urine is a valuable resource for nutrient recovery. Stabilization is, however, recommended to prevent urea hydrolysis and the associated risk for ammonia volatilization, uncontrolled precipitation, and malodor. This can be achieved by alkalinization and subsequent biological conversion of urea and ammonia into nitrate (nitrification) and organics into CO2. Yet, without pH control, the extent of nitrification is limited as a result of insufficient alkalinity. This study explored the feasibility of an integrated electrochemical cell to obtain on-demand hydroxide production through water reduction at the cathode, compensating for the acidification caused by nitritation, thereby enabling full nitrification. To deal with the inherent variability of the urine influent composition and bioprocess, the electrochemical cell was steered via a controller, modulating the current based on the pH in the bioreactor. This provided a reliable and innovative alternative to base addition, enabling full nitrification while avoiding the use of chemicals, the logistics associated with base storage and dosing, and the associated increase in salinity. Moreover, the electrochemical cell could be used as an in situ extraction and concentration technology, yielding an acidic concentrated nitrate-rich stream. The make-up of the end product could be tailored by tweaking the process configuration, offering versatility for applications on Earth and in space.

A mechanistic understanding of the nitrification sand layer performance in a nitrogen removing biofilter (NRB) treating onsite wastewater

Bench-scale columns were used to test the impact of depth, alkalinity, and nitrogen/hydraulic loading on nitrification performance and microbial community abundance in a sand filter treating onsite wastewater. The extent of nitrification was independent of the column depth at the test hydraulic loading rate (20.5 L m−2 d−1), as full nitrification was observed at 15 cm of the column. The nitrification performance was less sensitive to nitrogen loading increase (0.15 to 0.53 mg N cm−2 d−1), while increased hydraulic loading (from 20.5 L m−2 d−1 to 32.8 L m−2 d−1) and insufficient alkalinity caused reduced nitrification at shallow column depth. Microbial analysis suggested the majority of biomass and functional species were present at the top 15 cm, with several orders of magnitude lower microbial density was observed at 45 cm depth. In addition, the microbial community present in the aged sand matrix could sustain efficient nitrification when treating synthetic wastewater. Collectively, these findings reveal the precise conditions for optimizing for complete nitrification of wastewater by sand filters.

Controls and Adaptive Management of Nitrification in Agricultural Soils.

Agriculture is responsible for over half of the input of reactive nitrogen (N) to terrestrial systems; however improving N availability remains the primary management technique to increase crop yields in most regions. In the majority of agricultural soils, ammonium is rapidly converted to nitrate by nitrification, which increases the mobility of N through the soil matrix, strongly influencing N retention in the system. Decreasing nitrification through management is desirable to decrease N losses and increase N fertilizer use efficiency. We review the controlling factors on the rate and extent of nitrification in agricultural soils from temperate regions including substrate supply, environmental conditions, abundance and diversity of nitrifiers and plant and microbial interactions with nitrifiers. Approaches to the management of nitrification include those that control ammonium substrate availability and those that inhibit nitrifiers directly. Strategies for controlling ammonium substrate availability include timing of fertilization to coincide with rapid plant update, formulation of fertilizers for slow release or with inhibitors, keeping plant growing continuously to assimilate N, and intensify internal N cycling (immobilization). Another effective strategy is to inhibit nitrifiers directly with either synthetic or biological nitrification inhibitors. Commercial nitrification inhibitors are effective but their use is complicated by a changing climate and by organic management requirements. The interactions of the nitrifying organisms with plants or microbes producing biological nitrification inhibitors is a promising approach but just beginning to be critically examined. Climate smart agriculture will need to carefully consider optimized seasonal timing for these strategies to remain effective management tools.

Prolonged exposure of mixed aerobic cultures to low temperature and benzalkonium chloride affect the rate and extent of nitrification

The combined effect of benzalkonium chloride (BAC) and prolonged exposure to low temperature on nitrification was investigated. Ammonia oxidation at 22–24°C by an enriched nitrifying culture was inhibited at increasing BAC concentrations and ceased at 15mg BAC/L. The non-competitive inhibition coefficient was 1.5±0.9mg BAC/L. Nitrification tests were conducted without and with BAC at 5mg/L using an aerobic, mixed heterotrophic/nitrifying culture maintained at a temperature range of 24–10°C. Maintaining this culture at 10°C for over one month in the absence of BAC, resulted in slower nitrification kinetics compared to those measured when the culture was first exposed to 10°C. BAC was degraded by the heterotrophic population, but its degradation rate decreased significantly as the culture temperature decreased to 10°C. These results confirm the negative impact of quaternary ammonium compounds on the nitrification process, which is further exacerbated by prolonged, low temperature conditions.

Dynamics of ammonia-oxidizing archaea and bacteria in relation to nitrification along simulated dissolved oxygen gradient in sediment–water interface of the Jiulong river estuarine wetland, China

Dissolved oxygen (DO) is a very important factor controlling the nitrogen cycle in wetlands. However, it is still unclear to what extent the presence of ammonia-oxidizing archaea (AOA) and bacteria (AOB), and related nitrification, are influenced by DO in estuarine wetlands. The aims of this study were to determine changes of nitrification at the sediment–water interface, to examine the abundance and diversity of archaeal and bacterial ammonia oxidizers in estuarine sediments, and to identify the correlation between nitrification and ammonia-oxidizing microorganisms along a simulated dissolved oxygen gradient in a Chinese estuarine wetland. The results showed that the nitrification rate was positively correlated with the diversity and abundance of AOA but not AOB, and the abundance and diversity of AOA can explain 87 % of the total variance of the first axes in the redundancy analysis. This indicates that AOA were primarily involved in ammonia oxidation in this study. Additionally, AOB were much more influenced by DO than AOA inferred from the assessment of dominant species and principal coordinates analysis of AOA and AOB. Higher diversity and abundance of AOA occurred in the mangrove sediments, which explain the higher nitrification rates in the mangrove sediments compared to the bare mudflat sediments. Notably, the trend of nitrification rate in the bare mudflat sediments was different from that in the mangrove sediments, suggesting that the extent of nitrification as impacted by DO depends largely on the sediment biotic and nutrient properties, and its environmental conditions including DO levels.

Application of struvite precipitation coupled with biological treatment to slaughterhouse wastewaters

In this study, struvite precipitation coupled with an activated sludge process was applied to slaughterhouse wastewaters. Biological treatability characteristics of the wastewater were evaluated in a wide organic loading range of 0.06–0.42 g COD (g MLVSS)−1d−1 to assess COD removal as well as the extent of nitrification. Results of biological treatment of raw wastewater indicated that COD removal varied between 88% and 99% and complete nitrification was achieved at 0.1 g COD (g MLVSS)−1d−1 and lower organic loadings. Biological treatment of the struvite‐precipitated sample, which required no nitrification, yielded 86% COD removal at the organic removal of 0.3 g COD (g MLVSS)−1d−1. Struvite precipitation of both raw and biologically treated wastewater was at effective stoichiometric magnesium and phosphate doses to ammonia and between pH values of 9.0 and 9.5, providing ammonia concentrations of 20–30 mg N L−1 in the effluent and being independent of initial concentrations. The application of struvite precipitation both prior to and after biological treatment resulted in similar effluent qualities and provided the additional benefit of having a high‐rate activated sludge system instead of a low organic loading system with nitrification–denitrification. An additional benefit of struvite precipitation was the production of sludge which had recovery potential as a fertilizer. Among the tested treatment schemes, biological treatment following struvite precipitation seemed to be more advantageous in terms of process stability.

Immobilization of nitrifying bacterial consortia on wood particles for bioaugmenting nitrification in shrimp culture systems

Shrimp grow out systems under zero water exchange mode demand constant remediation of total ammonia nitrogen (TAN) and NO2−– N to protect the crop. To address this issue, an inexpensive and user-friendly technology using immobilized nitrifying bacterial consortia (NBC) as bioaugmentors has been developed and proposed for adoption in shrimp culture systems. Indigenous NBC stored at 4 °C were activated at room temperature (28 °C) and cultured in a 2 L bench top fermentor. The consortia, after enumeration by epifluorescence microscopy, were immobilized on delignified wood particles of a soft wood tree Ailantus altissima (300–1500 μm) having a surface area of 1.87 m2 g−1. Selection of wood particle as substratum was based on adsorption of NBC on to the particles, biofilm formation, and their subsequent nitrification potential. The immobilization could be achieved within 72 h with an initial cell density of 1×105 cells mL−1. On experimenting with the lowest dosage of 0.2 g (wet weight) immobilized NBC in 20 L seawater, a TAN removal rate of 2.4 mg L−1 within three days was observed. An NBC immobilization device could be developed for on site generation of the bioaugmentor preparation as per requirement. The product of immobilization never exhibited lag phase when transferred to fresh medium. The extent of nitrification in a simulated system was two times the rate observed in the control systems suggesting the efficacy in real life situations. The products of nitrification in all experiments were undetectable due to denitrifying potency, which made the NBC an ideal option for biological nitrogen removal. The immobilized NBC thus generated has been named TANOX (Total Ammonia Nitrogen Oxidizer).

Lead Contamination of Potable Water Due to Nitrification

Nitrification can increase levels of soluble lead in potable water by reducing pH. The magnitude of the pH drop depends on the initial alkalinity and extent of nitrification. At 100 mg/L alkalinity as CaCO3, complete nitrification did not significantly decrease pH (pH stayed >7.5) or increase lead contamination of water for lead pipe, but at 15 mg/L alkalinity, nitrification decreased the pH by 1.5 units (pH reduced to <6.5) and increased soluble lead contamination by 65 times. Lower pH values from nitrification also leached 45% more lead and 81% more zinc from leaded brass connected to PVC pipes relative to the same situation for copper pipes. Particulate lead leaching was high but did not vary dependent on nitrification. While nitrification also produces nitrite and nitrate and reduces inorganic carbon and dissolved oxygen, these factors did not significantly impact lead leaching in this work.

Biological Decolorization of Reactive Anthraquinone and Phthalocyanine Dyes Under Various Oxidation–Reduction Conditions

The decolorization of two anthraquinone dyes (Reactive Blue 4 [RB4] and Reactive Blue 19 [RB19]) and two phthalocyanine dyes (Reactive Blue 7 [RB7] and Reactive Blue 21 [RB21]) was investigated at an initial dye concentration of 300 mg/L using an unacclimated, enrichment culture. The culture was fed a mixture of organic compounds and maintained initially under aerobic conditions, and then progressively developed anoxic/ anaerobic conditions. Biotransformation-related decolorization of the dyes did not take place under aerobic conditions, but use of the feed organic mixture and biomass production by the enrichment culture were not affected. Complete ammonia removal occurred in the control and all dye-amended cultures. The development and extent of nitrification were much lower in the latter cultures, in which ammonia removal via air stripping was the dominant mechanism. Prolonged incubation of the culture under anoxic/anaerobic conditions with multiple carbon source additions resulted in a high decolorization extent of anthraquinone dyes (over 84%) and only partial decolorization of phthalocyanine dyes (49 to 66%). Development of significant methanogenic activity took place in the control and, to a lesser extent, in the two phthalocyanine dye-amended cultures, but the anthraquinone dyes severely inhibited the development of methanogenic activity. The RB4 and RB19 decolorization was attributed to nonreversible, microbially mediated dye transformation(s), demonstrated by the accumulation of decolorization products with absorbance maxima in the 420- to 460-nm region. The decolorization of RB4 and RB19 followed Michaelis-Menten kinetics. At an initial dye concentration of 300 mg/L, the observed maximum decolorization rate per unit biomass was 9.1 and 37.5 mg dye/mg volatile suspended solids x day for the RB4 and RB19, respectively. Thus, partial decolorization of reactive phthalocyanine dyes and extensive biological decolorization of reactive anthraquinone dyes is feasible only under anoxic/anaerobic conditions.

Feasibility of controlling nitrification in predenitrification plants using DO, pH and ORP sensors

Experimental studies were carried out on a bench-scale nitrogen removal system with a predenitrification configuration to gain insights into the spatial and temporal variations of DO, pH and ORP in such systems. It is demonstrated that these signals correlate strongly with the operational states of the system, and could therefore be used as system performance indicators. The DO concentration in the first aerobic zone, when receiving constant aeration, and the net pH change between the last and first aerobic zones display strong correlations with the influent ammonia concentration for the domestic wastewater used in this study. The pH profile along the aerobic zones gives good indication on the extent of nitrification. The experimental results also showed a good correlation between ORP values in the last aerobic zone and effluent ammonia and nitrate concentrations, provided that DO in this zone is controlled at a constant level. These results suggest that the DO, pH and ORP sensors could potentially be used as alternatives to the on-line nutrient sensors for the control of continuous systems. An idea of using a fuzzy inference system to make an integrated use of these signals for on-line aeration control is presented and demonstrated on the bench-scale system with promising results. The use of these sensors has to date only been demonstrated in intermittent systems, such as sequencing batch reactor systems.

Performance of a pilot-scale high rate algal pond system treating abattoir wastewater in rural South Australia: nitrification and denitrification

As part of a study examining the efficacy of high-rate algal pond treatment of high-strength abattoir wastewater, the impact of pond configuration and loading rate on nitrification was determined. The extent of nitrification in all ponds was consistent with mass balance estimates of oxygen demand and availability. Deeper ponds were more stable nitrifying systems, with shallow ponds displaying greater variation in response to changes in nitrogen loading. In a separate experiment the pond system was modified by covering a part of an in-series HRAP to exclude light, providing conditions suitable for denitrification. Specific denitrification rates were often within the range typical for endogenous carbon sources, with mass balance calculations indicating removals of up to 95%.

Assessment of Contamination By Percolation Of Septic Tank Effluent Through Natural and Amended Soils

Fly ash has been found to be a potential material for the treatment of municipal and industrial wastewater, and may be useful in the treatment of septic tank effluent. Laboratory columns (30 cm) were used to determine the sorption capacity and hydraulic properties of lagoon fly ash, loamy sand, sand, and sand amended by lagoon fly ash (30 and 60%) and red mud gypsum (20%). The removal of chemical oxygen demand (COD) was high in all column effluents (71-93%). Extent of nitrification was high in Spearwood sand, Merribrook loamy sand and 20% red mud gypsum amended Spearwood sand. However, actual removal of nitrogen (N) was high in columns containing lagoon fly ash. Unamended Spearwood sand possessed only minimal capacity for P sorption. Merribrook loamy sand and red mud gypsum amended sand affected complete P removal throughout the study period of 12 weeks. Significant P leakage occurred from lagoon fly ash amended sand columns following 6-10 weeks of operation. Neither lagoon fly ash nor red mud gypsum caused any studied heavy metal contamination including manganese (Mn), lead (Pb), zinc (Zn), cadmium (Cd) and chromium (Cr) of effluent. It can be concluded that Merribrook loamy sand is better natural soil than Spearwood sand as a filter medium. The addition of lagoon fly ash enhanced the removal of P in Spearwood sand but the efficiency was lower than with red mud gypsum amendment.

Occurrence of nitrification in chloraminated distribution systems

Data from US distribution systems that chloraminate are evaluated as predictors of nitrification.Utilities in the United States that chloraminate were surveyed to evaluate the incidence of nitrification in distribution systems and determine whether nitrification can be predicted from basic system and water quality data. An estimated two thirds of medium and large US systems that chloraminate experience nitrification to some degree. About every fourth surveyed utility reported moderate to severe nitrification problems. In addition, every fourth utility did not know the extent of nitrification in its system. The incidence of nitrification was more frequent during summer or when the temperature was greater than 15°C (59°F); nevertheless, several sites sampled under cold water conditions—i.e., below 10°C (50°F)—also evidenced nitrification. No one water quality parameter by itself may be a good indicator of nitrification, but several important factors should be evaluated collectively—nitrite, nitrate, chloramine dosage and residual, ammonia, pH, heterotrophic bacterial counts, and dissolved oxygen.

Nitrogen removal in a semi-continuous process

Laboratory tests using synthetic feed were conducted to evaluate the nitrogen removal capabilities of the continuously fed intermittently decanted (CFID) process. Experimental results were in general agreement with theoretically predicted values. Ammonia removal is governed by the extent of nitrification during aeration, and the level of leakage during settling and decantation. The former is controlled by the aerobic SRT, with the critical value being approx. 5 days at 13–18°C and <2.5 days at 25–26°C. Ammonia leakage is controlled by hydraulic parameters. For a given nominal hydraulic residence time, short cycle, short settling and short decantation times are conducive to low leakage. Total removal of nitrogen can be obtained if a well nitrifying system is allowed to denitrify. Denitrification is affected primarily by the anoxic fraction of the cycle. The specific denitrification rate ranged from 0.014 to 0.037 g N g SS −1 day −1, which is comparable to reported values for internal or endogenous denitrification in conventional systems.

Rates of nitrification, distribution of nitrifying bacteria, and nitrate fluxes in different types of sediment from Danish waters

Nitrification rates, measured in different sediment types from Danish waters, are in the range of 0.3 to 1.4 mmol NO 3 - m-2 d-1. There is no signification between sandy and muddy sediments, nor between shallow and deeper stations. The extent of nitrification is probably limited to the zone of oxygen penetration, 1.5 to 5.5 mm. There are, however, nitrifying bacteria located in the anoxic sediment layers. There relative numbers were found by measuring the “nitrification potential” of the sediment. These potential rates (22°C) can also be used to calculate actual rates of nitrification, by adjusting to in situ temperature and oxygen penetration. These calculated rates agree with the actual measured rates of nitrification for a wide range of sediment types and may be used for the estimation of actual nitrification rates. Nitrate flux out from the sediment/water interface is in the range of 0 to 0.7 mmol NO 3 - m-2 d-1. There is no correlation between concentration gradients of nitrate across the sediment/water interface and the measured flux of nitrate. Approximately 50% of nitrate production is released to the water column. The remainder (0 to 0.35 mmol N m-2 d-1) may have been denitrified.

Some observations on the biochemistry and inhibition of nitrification

The effects of compounds potentially toxic to nitrification were examined using a laboratory procedure which involved aerating activated sludge mixed liquors in the presence of measured amounts of these compounds. Results for a variety of compound types are given and the applicability of the procedure discussed. The results obtained for thiourea and its analogues provide further support for an hypothesis suggested as an explanation of the toxicity of compounds containing the NCS group; this is based on a model reaction involving copper in oxidases in Nitrosomonas. It is also suggested that the losses in inorganic nitrogen observed during nitrification (up to 43% and which are lowered as the extent of nitrification is lowered) might be due to a biochemical mechanism in which nitrous oxide is produced by Nitrosomonas from nitrite using a hydroxylamine-nitrite reductase. Recommendations indicating further laboratory and field studies are made.

Acceleration by montmorillonite of nitrification in soil.

A soil naturally containing montmorillonite (M) was amended with 10% M and sequentially perfused with glyeme, with fresh glyeme being added every 16--17d after nitrification of the previously added glycine-nitrogen had reached a plateau. In some systems, the old perfusates were replaced each time with a fresh glycine solution; in others, the initial perfusate was not replaced but only adjusted each time to the original 200 ml volume and a comparable glycine concentration (140 micrograms NH2-N/ml). The incorporation of M enhanced the rates of heterotrophic degradation of glycine and subsequent autotrophic nitrification, but these stimulatory effects decreased with each successive perfusion. The reasons for these decreases are not known, but they did not appear to be related to inorganic nutrition, as perfusion with a mixed cation solution after five perfusion cycles did not significantly enhance nitrification in either the check or M-amended soils during three subsequent perfusions with glycine. The enhancement of nitrification by M appeared to be a result, in part, of the greater buffering capacity of the M-amended soil, as indicated by lesser reductions in the pH of perfusates from the M-amended soil, by titration curves of the soils, and by the greater and longer stimulation of nitrification in the check soil amended with 1% CaCO3, which had a greater buffering capacity than did M. The stimulation by CaCO3 may also have been partially the result of providing CO2 for the autotrophic nitrifyers. Significant concentrations of nitrite accumulated only in perfusates from soil amended with CaCO3. Air-drying and remoistening the soils enhanced nitrification of subsequently added glycine, especially in the check soil. The importance of pH-mediation, of the production of inhibitors, and/or of feed-back inhibition was indicated by the lower rate and extent of nitrification in systems wherein the perfusates were not replaced between successive additions of glycine. Although the results of these studies confirmed previous observations that M enhances the rate of nitrification in soil, the mechanisms responsible for this stimulation are still not known.

Influence of Environmental Factors on the Nitrogen Cycle in Water

Understanding the behavior of impounded water is essential to the evaluation of any project involving streamflow regulation for water quality. Since 1962, the Engineering Activities Section of the Basic and Applied Sciences Program of the Federal Water Pollution Control Administration has been studying this subject, as specified in amended P.L. 87‐660. The study presented in this article was one in a series, designed to investigate the influence of natural environmental factors on the nitrogen cycle. There have been many studies of natural environments, but few controlled studies to demonstrate the influence of environmental factors on the rate and extent of nitrification. Equipment and methods are discussed, along with typical nitrification patterns, seed concentration, ammonia nitrogen concentration, relative turbulence, nitrites and nitrates, organics, and bacterial enumeration.

Effect of Nitrogen Volatilization on Soil Acidity Changes Due to Applied Nitrogen

AbstractNitrogen was applied as urea, NH4OH, (NH4)2SO4, (NH4)H2PO4, (NH4)2HPO4, NH4NO3, and NaNO3 to 10‐, 20‐, and 25‐g. samples of soil and incubated under conditions favorable for nitrification. Glucose was added during incubation to supply energy for denitrification. The samples were later analyzed for pH, NH4+, NO2‐, NO3‐, and organic N. The final acidities and extent of nitrification and volatilization varied considerably, even among identically treated samples. Volatilization losses of N ranged from none to the entire amount applied.The acidity resulting from nitrification was calculated for each sample and compared to actual acidity. The difference between calculated and observed acidity was accounted for by equivalent N volatilization. This relationship was obtained with 3 soils regardless of the N source applied and the probable gaseous form of loss.